1. Field of the Invention
The present invention pertains to coupling apparatus for coupling two objects together in tandem. For example, the apparatus may be used to couple a trailer to a tractor, to couple several trailers to one another, to couple a floating vessel to another or to a dock, etc. In particular, the invention pertains to an improved "one point" type coupling as opposed to a two or three point coupling. Such apparatus generally comprises two main portions or coupling means each of which is carried by a respective one of the two objects.
In such applications, it is highly desirable and, in most cases, necessary that the coupling apparatus provide for universal movement between the two objects, i.e. for relative pivoting about three generally mutually perpendicular axes. For example, where a trailer or other vehicle is being drawn by a tractor or other prime mover, it must be able to pivot about a generally vertical axis so as to follow the tractor as it turns corners, to pivot about a generally transverse horizontal axis so as to ride over bumps and concavities in the road or ground on which it is traveling, and to pivot about a generally longitudinal horizontal axis so as to permit rocking movement where the road or ground is uneven. Similar movements must be permitted between a floating vessel and another vessel or a dock to allow one vessel to follow the other and/or to allow the vessel to move with the wave action of the water.
Another highly desirable feature of coupling apparatus of the type described above is that it should be possible for coupling and uncoupling to be carried out by a single operator. Furthermore, the operator should be able to couple and uncouple the two objects automatically without the necessity of leaving his position, as in the driver's seat of the tractor, and/or of directly manually handling the coupling means.
2. Description of the Prior Art
My copending application Ser. No. 550,854, filed Feb. 18, 1975, now U.S. Pat. No. 3,981,517, and which is a continuation-in-part of my prior U.S. Pat. No. 3,866,948, discloses several embodiments of coupling apparatus of the type described above which achieve the objects of universal movement and automatic latching. In each of these two embodiments there is, in the first coupling means on the first object, an extendable mechanism which is longitudinally extendable and retractable with respect to the first object by drive means such as a double acting hydraulic piston and cylinder. The latching means includes a pair of dogs carried by the extendable mechanism and each integrally attached to a pivotable cam plate. A latch control means on the extendable mechanism may be extended away from the first object by the drive means separately from the remainder of the extendable mechanism, and this extension causes pivoting of the cam plates to move the dogs laterally outwardly and into mating apertures in the second coupling means. When the dogs and apertures are engaged, the latch control means is stopped aginst further individual extension so that further operation of the drive means extends the entire extendable mechanism as a unit. This effects uncovering of a universal joint so that it can pivot freely.
My prior coupling apparatus was designed primarily for use in applications in which the tractor or other prime mover was provided with an integral drawbar of the conventional type rigidly attached to the tractor as an integral part thereof. Consequently, the coupling means to be carried by the tractor is formed in such a way that it could be attached to such a drawbar. While this is an advantage in that it allows existing tractors and other prime movers to be easily converted for use of the coupling means, it is a disadvantage in that the resulting composite structure is somewhat bulky and inconvenient and may also be complicated by a larger number of parts than is strictly necessary.
Another problem with the above apparatus is that the lateral movement of the dogs is directed only by the cam plates in their pivotal movement. The cam plates in turn ride relatively freely between the latch control means and the remainder of the extendable mechanism and are not attached to either of these parts as firmly as might be desired. Thus, with the prior mechanism, there is a chance of dislodging and/or jamming of the cam plates and dogs and of misalignment of the dogs with the apertures into which they must pass, particularly if the cam plates should be accidentally bent. Furthermore, in at least some of the embodiments of the above apparatus, the cam plates and dogs are in an exposed position on the outside of the coupling means and thus vulnerable to jamming by dirt, damage through physical jarring, exposure to rain causing rust, etc.
Another problem with the above apparatus is that, once the latch means are engaged, the universal joint and its control assembly must be relatively extended by a distance substantially equal to the length of the universal joint in order to allow complete universal movement. Thus, the coupling apparatus is relatively large or bulky when the joint is in its free position, and where a hydraulic ram assembly is used as the drive means, requires a relatively large, long stroke ram.